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View Full Version : Solved What did I do to my PropBOE?



Duane Degn
03-26-2012, 12:44 AM
I was atempting to power my new PropBOE with a LiPo battery pack. Most of my LiPo packs have Dean's connectors on them. I made an adapter to go from the Dean's connector to a center positive barrel jack.

While I was plugging in the barrel jack the ground of the the connector touched the positive 9V battery connector.

http://forums.parallax.com/attachment.php?attachmentid=91001&d=1332715119

Here's a picture of the connector partially inserted into the power connector. You can see the barrel jack comes very close to the 9V connector. With a little sideways force the two connectors will touch.

I pulled out a BS2 BOE to see how the two sets of power connectors were arranged. The distance between the connectors on the board seemed about the same but the angle of the barrel jack connector on the BS2 BOE is parallel with the side of the board. When I tried to push the barrel jack against the 9V connector using the same sideways force as I has used with the PropBOE, the two connectors did not touch.

Here's a picure of the barrel jack partially inserted into the BS2 BOE's connector. You can see there is more space between the protruding barrel jack and the 9V connector on this board than on the PropBOE.

http://forums.parallax.com/attachment.php?attachmentid=91003&d=1332715181

I think part of the problem is my PropBOE's barrel jack connector isn't completely parallel with the side of the board. You can see how it's slightly angled in this picture.

http://forums.parallax.com/attachment.php?attachmentid=91002&d=1332715141

I think in the future, I'll just put some heat shrink tubing over the 9V connectors.

My PropBOE still works when powered by USB. When I apply power to the barrel jack or 9V connectors, the PropBOE does not power up. The power LEDs remain off in both on positions of the switch.

It looks like the short caused some blistering of the PCB between the two connectors. You can kind of see the blister in this next picture.

91004

My hope is I just burned out a few parts (that I can replace) since the board still works with USB power.

According to the schematic the center pin of the barrel jack connector should be connected to the positive 9V connector. When I use my DMM with the positve lead on the positve 9V connector and the negative lead on the center pin of the barrel jack, the resistance reading jumps between about 500k ohm and an open circuit. If I switch the leads the resistance starts at about 360k ohm and steadily increases.

With the negative lead connected to ground, when I connect the positive lead to the center pin of the barrel jack connector, the resistance starts at about -170k ohms and steadily increases (gets less negative). If I reverse the leads, the resistance starts at about 150k ohms and steadily increases.

The grounds of both connectors are connected to ground.

Even if this problem is covered by the limited warranty, I'd rather fix my PropBOE if it can be done with a few parts instead of sending it back to Parallax. The PropBOE's power supply is a lot more complicated than the other Propeller boards I've used. I've been able to find and fix power supply problems on Propeller Proto Boards, but this power supply is beyond my present understanding.

Do any of you have suggestions of what could test to find the burnt out part(s)?

Edit: I've marked this thread solved since Ken is sending a replacement. I still don't know what parts I managed to fry.

evanh
03-26-2012, 01:04 AM
Looks to me like it's just the track between the two connectors that is fused. The power should work with one of them, either the barrel plug or the 9volt. Double check it. Make sure your power source is still working also.

I guess it's possible the track is T-shaped and the fusing has blown both paths. In this case you want to look at the schematics again and identify all the other parts connected to this one track. The objective here is to try to work out whether there is any other parts that have been severed along with the connectors - like the storage capacitor for example - and reconnect everything.

HShanko
03-26-2012, 02:46 AM
Oh Duane,

Such a sad, sad story. Not even a week old.

Guess those LIPO cells have a high short circuit current capacity, huh?

Ken Gracey
03-26-2012, 02:58 AM
I'm not sure I like the look of the 2.1 mm battery jack, slightly askew but also not the cause of the fatality. I'll get the crew to take a look at it since the PCB holes are normally sized to hold the component securely in position without the kind of angle I'm seeing. This board should be an artwork of workmanship from Rocklin.

I'll get you a replacement shipped out tomorrow, Duane based on workmanship. Bring the partially-damaged board to UPEW.

And be careful going forward with those 50A LIPOs!

Ken Gracey

Duane Degn
03-26-2012, 03:33 AM
Looks to me like it's just the track between the two connectors that is fused. The power should work with one of them, either the barrel plug or the 9volt. Double check it. Make sure your power source is still working also.

I guess it's possible the track is T-shaped and the fusing has blown both paths. In this case you want to look at the schematics again and identify all the other parts connected to this one track. The objective here is to try to work out whether there is any other parts that have been severed along with the connectors - like the storage capacitor for example - and reconnect everything.

Thanks for the suggestions Evan. I'm sure neither of the power connectors work. I've also tried several different power sources.

I'm pretty sure this is a four layer board which explains several things. One, why I'm having a hard time figuring out what is connected to what. And two, how Parallax got so many things on the board.



Oh Duane,

Such a sad, sad story. Not even a week old.

Guess those LIPO cells have a high short circuit current capacity, huh?

Yeah, I was kind of bummed. I'm working on a PropBOE-Bot (http://forums.parallax.com/showthread.php?138903-PropBOE-Bot)for my wife to use in the line following contest. (She is helping build the robot; she picks out the colors of the accessories.)


I'm not sure I like the look of the 2.1 mm battery jack, slightly askew but also not the cause of the fatality. I'll get the crew to take a look at it since the PCB holes are normally sized to hold the component securely in position without the kind of angle I'm seeing. This board should be an artwork of workmanship from Rocklin.

I'll get you a replacement shipped out tomorrow, Don based on workmanship. Bring the partially-damaged board to UPEW.

And be careful going forward with those 50A LIPOs!

Ken Gracey

Thanks Ken. This is great. This will allow me to still program the PropBOE while the other is on the way.

I hadn't planned on documenting my wife's PropBOE-Bot build but a couple of forum members have asked about code to use the PropBOE with a BOE-Bot so I thought I'd share what I was doing. I've since learned that Mike Green is making a PropBOE version (http://forums.parallax.com/showthread.php?138830-FemtoBasic-version-for-Propeller-Board-of-Education)of his FemtoBasic with BOE-Bot features.

Trying to follow traces on the board made me realize the PropBOE must be a four layer board. I had wondered how you managed to get all those IO pins routed to both the headers around the breadboard and also to the back "Surface Mount Playground".

I'll make sure and bring the damaged board with me to the Expo.

Thanks again for the replacement.

Ken Gracey
03-26-2012, 03:45 AM
Duane, apologies for identifying you as Don. Don is coming to UPEW.

Not sure if you've made the decision or not.

New board going to you tomorrow.

Ron Czapala
03-26-2012, 04:01 AM
The connector on my power supply is longer than needed and could possibly do the same thing. I think I better use a different one.

I wonder how hard it would be to swap the 9V connectors around on the next version...


http://forums.parallax.com/attachment.php?attachmentid=91011 91011

Phil Pilgrim (PhiPi)
03-26-2012, 04:11 AM
I wonder how hard it would be to swap the 9V connectors around on the next version...
Those connectors are arrayed that way for a reason: the arrangement prevents powering the board from both a battery and an external source at the same time.

-Phil

Ron Czapala
03-26-2012, 04:13 AM
Those connectors are arrayed that way for a reason: the arrangement prevents powering the board from both a battery and an external source at the same time.

-Phil

I know, but switching the positive and negative would still have the same effect. (Should have been more precise)

Phil Pilgrim (PhiPi)
03-26-2012, 04:20 AM
Oh, I thought you meant a more drastic rearrangement. Yes, your idea makes sense.

-Phil

Duane Degn
03-26-2012, 05:32 AM
Duane, apologies for identifying you as Don. Don is coming to UPEW.

Not sure if you've made the decision or not.

New board going to you tomorrow.

No problem Ken. I thought you were just calling me "sir" in Spanish. :smile:

My wife and I are both looking forward to attending the Expo.